Drive mechanisms suitable for use in drug delivery devices

ABSTRACT

The present disclosure is directed to a dose setting mechanism that may be used with a drug delivery device. The dose setting mechanism may include an inner body having a helical thread along an outer cylindrical surface of the inner body, and a drive sleeve for driving a piston rod in an axial direction, the drive sleeve positioned within at least a portion of the inner body. The dose setting mechanism may further include a dose dial sleeve rotatably engaged with the helical thread of the inner body and a dial grip connected to the dose dial sleeve and releasably connected to the drive sleeve. Further when a dose is set, the dial grip is rotated so that both the dose dial sleeve and the drive sleeve rotate with respect to the inner body.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of application Ser. No. 12/453,626,filed May 15, 2009 which is a continuation of application Ser. No.10/790,024, filed Mar. 2, 2004 which is now U.S. Pat. No. 7,553,299which claims priority to GB 0304823.8 filed on Mar. 3, 2003.

THE TECHNICAL FIELD OF THE INVENTION

The present invention relates to drive mechanisms suitable for use indrug delivery devices, in particular pen-type injectors, having dosagesetting means, enabling the administration of medicinal products from amulti-dose cartridge. In particular, the present invention relates tosuch drug delivery devices where a user may set the dose.

DESCRIPTION OF RELATED ART

Such drug delivery devices have application where regular injection bypersons without formal medical training occurs, i.e., patients. This isincreasingly common amongst those having diabetes where self-treatmentenables such persons to conduct effective management of their diabetes.

These circumstances set a number of requirements for drug deliverydevices of this kind. The device must be robust in construction, yeteasy to use in terms of the manipulation of the parts, understanding bya user of its operation and the delivery of the required dose ofmedicament. Dose setting must be easy and unambiguous. In the case ofthose with diabetes, many users will be physically infirm and may alsohave Impaired vision requiring the drive mechanism to have lowdispensing force and an easy to read dose setting display. Where thedevice is to be disposable rather than reusable, the device should becheap to manufacture and easy to dispose of (preferably being suitable,for recycling). To meet these requirements the number of parts requiredto assemble the device and the number of material types the device ismade from need to be kept to a minimum.

User operated drug delivery devices are well known within the medicalfield. WO9938554A2 teaches an injection syringe for apportioning setdoses of a medicine from a cartridge wherein a drive mechanismcomprising a unidirectional coupling (i.e., a ratchet) is disclosedwhich allows correction of a set overdose without dispensing the setamount of fluid or requiring the dismantling of the cartridge.

EP0937471A2 discloses a medication delivery pen having a drive mechanismcomprising a unidirectional coupling (i.e, a ratchet) located betweenthe rod barrel tube and the housing. The disclosed drive mechanism is ofthe direct type, which means that relatively high actuation force isrequired by the user.

Surprisingly it was found that a drive mechanism comprising aunidirectional coupling and a clutch mechanism according to instantinvention provides lower actuation forces for the user or,alternatively, allows application of greater volumes of medicinalproducts. Additionally the drive mechanism of instant invention providesthe advantage of intuitive, safe, and easy to use correction of a setdose and it further provides improved protection of the working partsfrom dust and debris.

DESCRIPTION OF THE INVENTION

Therefore, a first object of instant invention is a drive mechanism foruse in a drug delivery device comprising:

a housing having an internal and an external thread;

a piston rod having a non-circular cross section, and which isthreadedly engaged with the internal thread of the housing;

a unidirectional coupling located between the housing and the pistonrod;

a dose dial sleeve, which is threadedly engaged with the external threadof the housing and being rotatable with respect to the housing;

a drive sleeve, located between the housing and the piston rod, which Isaxially displaceable but not rotatable with respect to the piston rod;and

a clutch means located between the drive sleeve and the dose dialsleeve, which

-   -   a. when the dose dial sleeve and the drive sleeve are de-coupled        by the said clutch means, rotation of said dose dial sleeve with        respect to said drive sleeve is allowed; and    -   b. when the dose dial sleeve and drive sleeve are coupled by the        said clutch means rotation of the does dial sleeve with respect        to the said drive sleeve is prevented.

The term “drug delivery device” according to instant invention shallmean a single-dose or multi-dose, disposable or re-useable devicedesigned to dispense a selected dose of a medicinal product, preferablymultiple selected doses, e.g. insulin, growth hormones, low molecularweight heparins, and their analogues and/or derivatives etc. Said devicemay be of any shape, e.g. compact or pen-type. Dose delivery may beprovided through a mechanical (optionally manual) or electrical drivemechanism or stored energy drive mechanism, such as a spring, etc. Doseselection may be provided through a manual mechanism or electronicmechanism. Additionally, said device may contain components designed tomonitor physiological properties such as blood glucose levels, etc.Furthermore, the said device may comprise a needle or may beneedle-free. In particular, preferred embodiment the term drug deliverydevice shall mean a disposable multi-dose pen-type device havingmechanical and manual dose delivery and dose selection mechanisms, whichis designed for regular use by persons without formal medical trainingsuch as patients. Preferably, the drug delivery device is of theInjector-type. Optionally, the drug delivery device according to instantinvention further comprises a nut threadedly connected to the drivesleeve and rotatable with respect to the drive sleeve and which isengaged with the dose dial sleeve to allow axial displacement of the nutwith respect to the dose sleeve, but not rotation of the nut withrespect to the dose dial sleeve.

The term “housing” according to instant invention shall preferably meanan exterior housing (“main housing”, “body, “shell”) or interior housing(“inner body”, “Insert”) having an internal and an external thread. Thehousing may be designed to enable the safe, correct, and comfortablehandling of the drug delivery device or any of its mechanisms. Usually,it is designed to house, fix, protect, guide,

and/or engage with any of the inner components of the drug deliverydevice (e.g., the drive mechanism, cartridge, plunger, piston rod) bylimiting the exposure to contaminants, such as liquid, dust, dirt etc.In general, the housing may be unitary or a multipart component oftubular or non-tubular shape. Usually, the exterior housing serves tohouse a cartridge from which a number of doses of a medicinal productmay by dispensed.

In a more specific embodiment of instant invention, the interior housingis provided with a plurality of maximum dose stops adapted to be abuttedby a radial stop provided on the dose dial sleeve.

In a more particular embodiment of instant invention, the interiorhousing comprises a web having an opening through which the piston mayextend. A first cylindrical portion may extend from from the first endof the web, and a second and a third cylindrical portion may extend fromthe second end of the web. Preferably, the second cylindrical portion isprovided with an internal thread.

In a further embodiment of Instant invention, the insert comprises a webhaving an opening through which the piston may extend. A firstcylindrical portion may extend from a first end of the web, a bossprovided on a second end of the web and a cylindrical portion extendingaway from the web about a periphery of the boss. Optionally, the boss isprovided with an internal thread or a radial flange being spaced fromthe web with a cylindrical portion extending away from the web about aperiphery of the radial flange

The term “engaged” according to instant invention shall particularlymean the interlocking of two or more components of the drivemechanism/drug delivery device, e.g. a spline or thread connection,preferably the interlocking of helical threads of components(“threadedly engaged”).

The term “thread” according to instant invention shall preferably mean afull or part thread, e.g., a cylindrical spiral rib/groove, usually ofhelical nature, located on the internal and/or external surface of acomponent of the drug delivery device (“internal thread” and/or“external thread”), having an essentially triangular or square orrounded section designed to allow continuous free rotational and/oraxial movement between components. Optionally, a thread may be furtherdesigned to prevent rotational or axial movement of certain componentsin one direction.

The term “dose dial sleeve” according to instant invention shall mean anessentially tubular component of essentially circular cross-sectionhaving either:

-   -   a. a) both an Internal and external thread, or    -   b. b) an internal thread, or    -   c. c) an external thread,        said dose dial sleeve may be made or constructed of one or more        parts. Preferably, the “dose dial sleeve” according to instant        invention comprises an internal helical thread, which is        threadedly engaged with the external thread of the housing,        particularly the insert.

In yet another preferred embodiment the dose dial sleeve is designed toindicate a selected dose of a dispensable product. In still anotherpreferred embodiment of instant invention, the maximum selectable dosemay be determined by the abutment of a radially directed lug on the dosedial sleeve with a catch means on the insert following the maximumangular displacement of the dose dial sleeve with respect to thehousing. Preferably, the radially directed lug extends parallel to alongitudinal axis of the dose dial sleeve.

Generally, the term “catch means” according to instant Invention shallmean any constructive feature, which serves as a counterpart to the lugon the dose dial sleeve and which is preferably located on the outersurface of the insert, and which together with the lug of the dose dialsleeve defines the maximum allowable dosage of the mechanism.Optionally, the catch means may be a groove extending about a centralland, e.g., a central land being wedge shaped such that a first edgeextends radially less far than a second opposite edge to define asloping surface between the first edge and the second edge.

Indication of the selected dose on the dose dial sleeve may be achievedby use of markings, symbols, numerals, etc., e.g., printed on theexternal surface of the dose dial sleeve or an odometer, or the like.

In a more specific embodiment of instant invention, the dose dial sleevecomprises a first section of a first diameter and a second section ofsecond diameter.

The term “lead” according to instant invention shall preferably mean theaxial distance a nut would advance in one complete revolution;preferably “lead” shall mean the axial distance through which acomponent having a helical thread, i.e., dose dial sleeve, piston rod,etc., of the drive mechanism travels during one rotation. Therefore leadis a function of the pitch of the thread of the relevant component.

The term “pitch” according to instant invention shall preferably meanthe distance between consecutive contours of the helical thread,measured parallel to the axis of the helical thread.

The term “drive sleeve” according to Instant invention shall mean anyessentially tubular component of essentially circular cross-section andwhich is further located between the housing, preferably the internalhousing and the piston rod, and which is axially displaceable but notrotatable with respect to the piston rod. The drive sleeve of theinvention is further releasably connected to the dose dial sleeve by aclutch means and is further engaged with the piston rod at the distaland/or proximal end. The drive sleeve may further comprise a firstsection of the first diameter located between the insert and the pistonrod and a second section of second diameter located between the pistonrod and the dose dial sleeve.

The term “releasibly connected” according to instant invention shallpreferably mean that two components of instant mechanism or device arereversibly joined to each other, which allows coupling and decoupling,e.g., by means of a clutch.

The term “piston rod” according to instant invention shall mean acomponent adapted to operate through/within the housing, designed totranslate axial movement through/within the drug delivery device,preferably from the drive sleeve to the piston, for the purpose ofdischarging/dispensing an injectable product. Said piston rod may beflexible or not. It may be a simple rod, a lead-screw, or the like. The“piston rod” according to instant invention shall further mean acomponent having a non-circular cross-section and an external threadlocated on its first end. It may be made of any suitable material knownby a person skilled in the art.

The term “first end” according to instant invention shall mean theproximal end. The proximal end of the device or a component of thedevice shall mean the end, which is closest to the dispensing end of thedevice.

The term “second end’ according to instant invention shall mean thedistal end. The distal end of the device or a component of the deviceshall mean the end, which is furthest away from the dispensing end ofthe device.

The term “clutch means” according to instant invention shall mean anymeans, which releasibly connects the dose dial sleeve and the drivesleeve and which is located between the drive sleeve and the dose dialsleeve, and which allows rotation of the dose dial sleeve with respectto said drive sleeve when the dose dial sleeve and the drive sleeve arede-coupled, and which prevents rotation of the dose dial sleeve withrespect to the drive sleeve when the dose dial sleeve and drive sleeveare coupled. According to instant Invention the term “clutch means”encompasses any clutch mechanism engaging for the purpose of reversiblylocking two components in rotation, e.g., by use of axial forces toengage a set of face teeth (saw teeth, dog teeth, crown teeth) or anyother suitable frictional faces.

In still another embodiment of instant invention, the drive mechanismfurther comprises a clicker means. Preferably, the “clicker means” shallmean any means located between the dose dial sleeve and the drivesleeve, which upon relative rotation of the said drive sleeve and thesaid dose dial sleeve causes a series of audible and/or tactile clicks.

Such a clicker means may comprise a plurality of longitudinallyextending teeth and a flexible toothed member, one of the plurality ofteeth and the toothed member being provided on the dose dial sleeve, theother being provided on the drive sleeve.

The term “unidirectional coupling” according to instant invention shallmean any mechanism located between the housing and the piston rod, whichallows movement of the piston rod in the proximal direction and preventsmovement of the piston rod in the distal direction, preferably actingbetween the non-circular cross section of the piston rod and thehousing.

A second aspect of Instant invention provides an assembly for use in adrug delivery device comprising the drive mechanism according to instantinvention.

A third aspect of the present invention provides a drug delivery devicecomprising the drive mechanism or the assembly according to instantinvention.

A fourth aspect of the present invention provides a method of assemblinga drug delivery device comprising the step of providing a drivemechanism or an assembly according to instant invention.

A fifth aspect of instant invention is the use of a drug delivery deviceaccording to instant Invention for dispensing a medicinal product,preferably dispensing a pharmaceutical formulation (e.g. solution,suspension etc.) comprising an active compound selected from the groupconsisting of insulin, growth hormone, low molecular weight heparin,their analogues and their derivatives.

BRIEF DESCRIPTION OF THE DRAWINGS

Without any limitation, the instant invention will be explained ingreater detail below in connection with a preferred embodiment and withreference to the drawings in which:

FIG. 1 shows a sectional view of a first embodiment of the drug deliverydevice, in accordance with the present invention in a first, cartridgefull, position;

FIG. 2 shows a sectional view of the drug delivery device of FIG. 1 in asecond, maximum first dose dialed, position;

FIG. 3 shows a sectional view of the drug delivery device of FIG. 1 in athird, maximum first dose dispensed, position;

FIG. 4 shows a sectional view of the drug delivery device of FIG. 1 in afourth, final dose dialed, position;

FIG. 5 shows a sectional view of the drug delivery device of FIG. 1 in afifth, final dose dispensed, position;

FIG. 6 allows a sectional view of a second embodiment of the drugdelivery device in accordance with the prevent invention;

FIG. 7 shows a sectional side view of a third embodiment of the drugdelivery device in accordance with the present invention;

FIG. 8 shows a perspective view of a dose dial sleeve for use inconjunction with the present invention;

FIG. 9 shows a perspective view of an insert for use with the dose dialsleeve of FIG. 8;

FIG. 10 shows a sectional side view of a fourth embodiment of the drugdelivery device in accordance with the present invention; and

FIG. 11 shows a sectional side view of a fifth embodiment of the drivemechanism according to instant invention in a first, cartridge full,position.

DETAILED DESCRIPTION OF THE EMBODIMENTS Example 1

Referring to FIGS. 1 to 5 there is seen a drug delivery device inaccordance with the first embodiment of the present invention. Thedevice comprises a housing 2 within which are located a cartridge 4containing medicinal product, means for setting or selecting the dose ofmedicinal product to be expelled and means for expelling the selecteddose of medicinal product. The housing 2 is generally cylindrical inshape and is divided into two compartments by a web 6 to be described inmore detail below. The cartridge 4 is located within a first part of thehousing 2. The dose setting means and the means for expelling theselected dose of medicinal product are retained; that is held, within asecond part of the housing 2. An advantage of a one piece housingenclosing the cartridge 4 together with the dose setting and doseexpelling means lies in the ease of assembly of the product. This is inpart due to the reduced number of components in the pen-type injector.Also, the unitary nature of the housing 2 means that the pen-typeinjector is mode robust.

The cartridge 4 may be secured in position in the first part of thehousing 2 by any suitable means. A needle unit may be secured to a firstend of the cartridge 4. A temporary covering 8 is shown in this positionin the Figures. The cartridge 4 further comprises a displaceable piston10. Advancing the piston 10 towards the first end of the cartridge 4causes the medicinal product to be expelled from the cartridge 4 throughthe needle unit. A cap 12 Is provided to cover the needle unit when theinjector is not in use. The cap 12 may be releasably secured to thehousing 2 by any suitable means.

The dose setting means and the mean for expelling the selected dose ofmedicinal product will now be described in more detail. The web 6dividing the housing 2 is a part of an insert 14 located within thehousing 2. The insert 14 comprises a first cylindrical portion 16extending from a first side of the web 6 and second and thirdcylindrical portions 18,20 extending from a second side of the web 6.The web 6 is provided with a circular opening 22 extending through theweb 6.

The first cylindrical portion 16 extends from a periphery of the web 6.The insert 14 is secured to the housing 2 by way of the firstcylindrical portion 16 by any suitable means. In the illustratedembodiment features 24 are provided within the housing 2 and on an outersurface of the first cylindrical portion 16 to enable the insert to be asnap fit to the housing 2.

The second cylindrical portion 18 extends a small distance from thesecond aide of the web 6 about a periphery of the opening 22. AnInternal surface of the second cylindrical portion Is provided With athread 26.

The third cylindrical portion 20 extends substantially within thehousing 2 from the second side of the web 6. The diameter of the thirdcylindrical portion 20 is such that a first channel 28 is formed betweenan outer surface of the second cylindrical portion 20 and an innersurface of the third cylindrical portion. A second channel 30 is formedbetween an outer surface of the third cylindrical portion 20 and thehousing 2.

A piston rod 32 extends through the opening in the web 6. The piston rod32 is generally elongate and is provided with a thread 34 extending froma first end of the piston rod 32. The thread 34 of the piston rod 32engages the thread of the Inner surface of the second cylindricalportion 18 of the insert 14. The first end of the piston rod 32 Isprovided with a pressure foot 36. In use the pressure foot 36 isdisposed on the first side of the web 6 to about the cartridge piston10.

Ratchet means 40 are located adjacent the web 6 on the first side of theweb 6. The ratchet means 40 serve the purpose of allowing the piston rod32 only to rotate through the insert 14 in a single direction. Due tothe one piece construction of the housing, the ratchet means can be madelarger than in known devices and so Is stronger (more rigid).

A dose dial sleeve 50 of generally cylindrical form comprises a firstsection of first diameter and a second section of second diameter. Thefirst section Is located within the second channel 30. An inner surfaceof the first section and the outer surface of the third cylindricalportion 20 are provided with interengaging features to provide a helicalthread 52 between the insert 14 and the dose dial sleeve 50. In theillustrated embodiment this was achieved by a helical track provided onthe outer surface of the third cylindrical portion 20 within which ahelical rib provided on the inner surface of the dose dial sleeve 50 mayrun. This enables the dose dial sleeve 50 to rotate about and along thethird cylindrical portion 20 of the insert 14.

An outer surface of the first section of the dose dial sleeve 50 isprovided with graphics 53. The graphics are typically a sequence ofreference numerals. The housing 2 Is provided with an aperture or window54 through which a portion of the graphics, representing a dosage valueselected by the user, may be viewed.

The graphics 53 may be applied to the dose dial sleeve 50 by anysuitable means. In the illustrated embodiment, the graphics 53 areprovided In the form of a printed label encircling the dose dial sleeve50. Alternatively the graphics may take the form of a marked sleeveclipped to the dose dial sleeve 50. The graphics may be marked in anysuitable manner, for example by laser marking.

It is an advantage of this arrangement that the helical thread 52 isformed within the dose dial sleeve between the dose dial sleeve and theinsert. As can be seen this means there is no direct route from outsidethe injector to the working surfaces of the helical thread. Should dustor dirt enter the pen this will tend to occur between the housing andthe dose dial sleeve where there are no working parts with which tointerfere. This is not the case for known devices In which a helicalthread Is formed between the housing and an interior moving surface. Inaddition because of the narrower diameter of the helical thread 52formed between the dose dial sleeve and the drive sleeve in comparisonto a similar thread formed between the housing and the dose dial sleeve,the helical thread 52 Is more efficient and easier to overhaul. Thisarrangement also produces an improvement in the dose size that can bedelivered for a particular linear travel of the dose expelling means.

The second section of the dose dial sleeve 50 is preferably of the sameouter diameter as the housing 2. Within the dose dial sleeve 50 there isa shoulder 56 between the first section of the dose dial sleeve 50 andthe second section of the dose dial sleeve 50.

A drive sleeve 60 of generally cylindrical form comprises a first partof first diameter and a second part of second diameter. A first end ofthe first part is located within the first channel 28 of the insert 14in the position shown in FIG. 1. The first part of the drive sleeve 60may be considered as comprising a first portion aligned with a secondportion. More generally in the position shown In FIG. 1 the firstportion of the drive sleeve 60 is located between the insert 14 and thepiston rod 32 while the second portion is located between the piston rod32 and the dose dial sleeve 50.

A second end of the piston rod 32 end en intimal surface of the drivesleeve 60 are splined together such that no relative rotation may occurbetween these parts, only longitudinal displacement.

The outer surface of the second portion of the first part of the drivesleeve 60 is provided with a helical thread 62. A nut 64 Is provided onthe helical thread 62 between the drive sleeve 60 and the dose dialsleeve 50. The dose dial sleeve 50 and the nut 64 arc splined togetherby spline means to prevent relative rotation between the nut 64 and thedose dial sleeve 50.

The second part of the drive sleeve 60 is of larger diameter then thefirst part of the drive sleeve 60. There is a step 66 between the firstpart of the drive sleeve 60 and the second part. The second part of thedrive sleeve 60 is seated within the second section of the dose dalsleeve 50. The shoulder 56 of the dose dial sleeve 50 and the step 66 ofthe drive sleeve 60 are adapted to be releasably engagable with oneanother to form a clutch means. When, as in FIG. 1, the dose dial sleeve50 and the drive sleeve 60 are not in engagement the dose dial sleeve 50is able to rotate with respect to the drive sleeve 60. Conveniently, theclutch means comprises a plurality of radially extending longitudinallydirected teeth provided respectively on the shoulder 56 of the dose dialsleeve 50 and the step 66 of the drive sleeve 60. When the dose dialsleeve 50 and the drive sleeve 60 are not forced together the respectiveteeth will ride over one another. Preferably, the radial separation ofthe respective teeth corresponds to a unit dosage.

The second part of the drive sleeve 60 further comprises a centralreceiving area 68 having a peripheral recess. A button 70 of generally“T” shaped configuration is provided, the stem of which is retainedwithin the receiving area. The stem of the button 70 Is provided with aperipheral bead 71 that Is retained in the peripheral recess, the button70 being able freely to rotate with respect to the. drive sleeve 60, butbeing retained axially therewith.

Clicker moans are provided between the second section of the dose dialsleeve 50 and the second part of the drive sleeve 60. In the illustratedembodiment, the internal surface of the second section of the dose dial50 is provided with a plurality of longitudinally extending teeth. Theradial separation of the teeth preferably corresponds to a unit dosage.The second part of the drive sleeve 60 carries a flexible toothed member72. Relative rotation between the dose dial sleeve 50 and the drivesleeve 60 will cause the flexible toothed member 72 to ride over theteeth to produce a series of clicks.

In FIG. 1, the injector is provided with!a filled cartridge 4. Tooperate the Injector a user must first select a dose. To set a dose thedose dial sleeve 50 is rotated by manipulating the second section of thedose dial sleeve 50 with respect to the housing 2 until the desired dosevalue is visible through the window 54. This action draws the dose dial50 along the second cylindrical portion of the insert 14. The drivesleeve 60 cannot rotate since it is splined to the piston rod 32. Thepiston rod 32 does not rotate due to the action of the ratchet means 40.The drive sleeve 60 is carried away from the web 6 along the piston rod32 by the dose dial sleeve 50 as the dose dial sleeve 50 moves out fromthe housing 2. The relative rotation between the dose dial sleeve 50 andthe drive sleeve 60 causes the flexible toothed member 72 to ride overthe ridges in the drive sleeve 60 to create a series of clicks. This Isan audible confirmation of the dose being dialed.

Since the nut 64 is splined to the dose dial sleeve 50, the relativerotation between the dose dial sleeve 50 and the drive sleeve 60 causesthe nut 64 to precess along the helical thread 62 of the drive sleeve60.

Once a desired dose has been set (as shown for example in FIG. 2), todeliver the dose the user depresses the button 70 to urge the button 70towards the first end of the housing 2. When the button 70 is depressedthe second part of the drive sleeve 60 is driven into the second sectionof the dose dial sleeve 50 to engage the clutch means therebetween toprevent relative rotation between the dose dial sleeve 60 and the drivesleeve 60. The drive sleeve 60 may still rotate with respect to thebutton 70. Further longitudinal movement of the button 70 causes thedose dial sleeve 50 (together with the drive sleeve 60) to rotatetowards the fire end of the injector. Since the piston rod 32 is splinedto the drive sleeve 60, the piston rod 32 is also rotated through theinsert 14 and the ratchet means 40 towards the first end of theinjector, thereby to advance the cartridge piston 10 and expel thedesired dose of medicinal product. The piston rod 32 continues toadvance until the drive sleeve 60 and dose dial sleeve 50 have returnedto their Initial positions (FIG. 3).

It can be seen that the dose selecting means and the dose expellingmeans extend beyond a second end of the housing 2 as the dose isselected and are returned within the housing 2 as the selected dose isexpelled.

Further dosages may be delivered as required. FIG. 4 shows en example ofa subsequently selected dosage. It will be noted that the nut 64 hasadvanced further along the helical thread 62 of the drive sleeve 60. Theposition of the nut 64 along the helical thread 62 corresponds to theamount of medicinal product remaining in the cartridge 4, such that whenthe nut 64 reaches the end of the helical thread 62 (in the illustratedembodiment adjacent to the step 66 of the drive sleeve 60) and canrotate no further this corresponds to no medicinal product remaining inthe cartridge 4. It will be seen that if a user seeks to select aquantity of medical product greater than that remaining in the,cartridge 4, this cannot be done since when the nut 64 stops rotatingthe dose dial sleeve 50 and the drive sleeve 60 will become lockedtogether preventing rotation of the dose dial sleeve 50 and setting of alarger dose. FIG. 5 shows an injector according to the present inventionin which the entire medical product within the cartridge 4 has beenexpelled.

A second embodiment of the present invention is disclosed in FIG. 6.Like reference numerals are used to refer to like parts as between thefirst and second embodiments.

The piston rod 32′ shown in FIG. 6 has e dual start thread. The pistonfoot 36′ is reversible. This has advantages in manufacture. As can beseen the structure of the insert 14′ has been revised. The first side ofthe web 6′ is substantially unchanged. The other side of the web is nowprovided with a boss 80. A cylindrical portion 20′ extends away from theweb 6′ about a periphery of the boss 80. Threaded opening 22′ extendsthrough the web 6′ and the boss 80. An end of the cylindrical portion20′ of the insert 14′ remote from the web 6′ is provided with a stop inthe form of a land 104.

The dose dial sleeve 50′ is of modified construction. The dose dialsleeve comprises a first cylindrical portion 84 rigidly connected to asecond generally cylindrical portion 86. An Inner surface of the firstcylindrical portion 84 and the outer surface of the cylindrical portion20′ of the insert 14′ are provided with interengaging features toprovide a helical thread 52′ between the insert 14′ and the dose dialsleeve 50′. An outer surface of the first cylindrical portion 84 isprovided with the dose graphics. The housing 2′ is provided with anaperture or window 54′ through which a portion of the graphics may beviewed.

The second generally cylindrical portion 88 comprises a firstcylindrical section 88 and a second cylindrical section 90. The firstsection 88 is rigidly keyed to an inner surface of the first portion 84of the dose dial sleeve 50′. The second section 90 Is preferably of thesame outer diameter as the housing 2′. Within the dose dial sleeve 50′there is a shoulder 50′ between the first section 86 and the secondsection 90.

A nut 64′ is provided on the helical thread 62′ between the drive sleeve60′ end the first cylindrical section 86 of the dose dial sleeve 50′.The first cylindrical section 88 and the nut 64′ are splined together byspline means to prevent relative rotation between the nut 64′ and thedose dial sleeve 50′.

The shoulder 56′ of the dose dial sleeve 50′ and a step 66′ of a drivesleeve 60′ are adapted to be releasably engagable with on another toterm a clutch means. When, as In FIG. 6, the dose dial sleeve 50′ andthe drive sleeve 60′ are not in engagement the dose dial sleeve 50′ isable to rotate with respect to the drive sleeve 60′. Conveniently, theclutch moans comprises a plurality of radially extending longitudinallydirected teeth provided respectively on the shoulder 56′ of the dosedial sleeve 50′ and the stop 88′ of the drive sleeve 60′. When the dosedial sleeve 50′ and the drive sleeve 80′ are not forced together therespective teeth will ride over one another.

It will be seen that the structure of the drive sleeve 60′ has also beenmodified. The second end of the piston rod 32′ is provided with ascooped surface within which a domed part 90 of the drive sleeve 60′ mayextend. The domed part 90 is centrally located within a second part ofthe drive sleeve 60′ at a first end of the receiving area.

The button 70′ is of generally “T” shaped configuration. The stem of thebutton 70′ is retained within the receiving area. The stem of the button70′ is provided with a peripheral bead 71′ that is retained in theperipheral recess, the button 70′ being able freely to rotate withrespect to the drive sleeve 60′, but being retained axially therewith.

When the button 70′ is depressed the drive sleeve 60′ is urged intocontact with the dose dial sleeve 50′ such that the clutch means areengaged. At the same time, the scooped surface of the piston rod 32′ andthe domed surface of the drive sleeve approach but do not contact oneanother. The advantage of this structure is that it enables the overalllength of the device to be reduced thereby enabling easier operation ofthe device when expressing fluid from a cartridge.

A further embodiment of the button 70″ and the dose dial sleeve 50″ canbe seen in FIG. 7. Again like reference numerals are used to refer tolike parts. In the embodiment of FIG. 7, the overall length of thedevice may be reduced still further. The second end of the piston rod32″ Is generally U-shaped. The limbs of the U-shape are received withina second part of the drive sleeve 60″. A central receiving area of thedrive sleeve 60″ is defined by limbs (not shown) located in use betweenthe limbs formed on the second end of the piston rod 32″. The button 70″is of generally “T” shaped configuration. The stem of the button 70″ isretained within the receiving area. The stem of the button 70″ Isprovided with a peripheral bead 71″ that is retained in the peripheralrecess, the button 70″ being able freely to rotate with respect to thedrive sleeve 60″, but being retained axially therewith.

The second generally cylindrically portion 80″ of the dose dial sleeve50″ comprises a first cylindrical section 88″ and a second cylindricalsection 90″ connected by a radial flange 92 extending from a part of thesecond section, the first section 88″ being rigidly keyed to an innersurface of the first portion 84″ of the dose dial sleeve 50″, and thesecond section 90″ being of the same outer diameter as the housing 2″.

In each of FIGS. 6 and 7, there is a further modification to each of thedose dial sleeve and the insert. This may be seen more clearly withreference to FIGS. 8 and 9.

At a first end of the dose dial sleeve there is located on an internalsurface a radially directed lug 100 extending generally parallel to alongitudinal axis of the sleeve. At a second end of the insert on anexternal surface thereof there is provided a catch means. The catchmeans comprises a groove 102 extending about a central land 104. Thecentral land 104 is generally wedge shaped such that a first edge 106nearer the start of the thread extends radially less far than a secondopposite edge 108 located further along the thread. A sloping surface110 is defined between the first edge 108 and the second edge 108. Thus,when the dose dial sleeve is assembled to the insert, by threading thedose dial sleeve onto the insert, the lug 100 passes over the first edge106 and over the sloping surface 110. As the lug 100 passes fully overthe land 104 some elastic deformation of the respective elements, thedose dial sleeve and the insert occurs. Once the lug 100 is over theland 104, the second edge 105 of the land 104 acts as a stop to preventremoval of the dose dial sleeve from the insert.

The location of the second edge 108 of the land 104 is convenientlychosen at a radial location corresponding to 80 units of medicinalproduct, that is the maximum dose available is 80 units when the dosedial sleeve is wound from the initial position shown in any of FIG. 1, 6or 7 to a fully extended position with the second edge 108 of the land104 contacting the lug 100.

A fourth embodiment of the present invention is disclosed in FIG. 10.Like reference numerals are used to refer to like parts.

As can be seen the structure of the insert 14′″ has been revised. Thefirst side of the web 6′″ substantially unchanged. The other side of theweb is now provided with a boss 80′″. A radial flange 112 extendsoutwardly from.the boss 80′″, the radial flange 112 being spaced fromthe web 6′″, and a cylindrical portion 20′″ extending away from the web6′″ about a periphery of the radial flange 110. A threaded opening 22′″extends through the web 6′″ and the boss 80′″.

The dose dial sleeve 50′″ is of modified construction. The dose dialsleeve 50′″comprises a first cylindrical portion 84′″ rigidly connectedto a second generally, cylindrical portion 86′″. An inner surface of thefirst portion 84′″ and the outer surface of the cylindrical portion 20′″of the insert 14′″ are provided with interengaging features to provide ahelical thread 52′″ between the insert 14′″ and the dose dial sleeve50′″. An outer surface of the first cylindrical portion 84′″ is providedwith the dose graphics. The housing 2′″ is provided with an aperture orwindow 54′″ through which a portion of the graphics may be viewed.

The second generally cylindrical portion 86′″ comprises a first innercylindrical section 88′″ and a second outer cylindrical section 90′″.The first section 88′″ is rigidly keyed to an inner surface of the firstportion 84′″ of the dose dial sleeve 50′″. The second section 90′″ ispreferably of the same outer diameter as the housing 2′″. Within thedose dial sleeve 50′″ there is a radial flange 94 extending between theouter section 90′″ and an intermediate part of the inner section 88′″.

A nut 64′″ is provided on a helical thread 62′″ formed on the drivesleeve 60′″. The nut 64′″ is disposed between the drive sleeve 60′″ andthe second cylindrical section 88′″ of the dose dial sleeve 50′″. Thesecond cylindrical section 88′″ and the nut 64′″ are keyed together byspline means to prevent relative rotation between the nut 64′″ and thedose dial sleeve 50′″.

An upper surface of the radial flange 94 of the dose dial sleeve 50′″and a step 66′″ of the drive sleeve 60′″ are adapted to be releasablyengagable with one another to form a clutch means. When, as in FIG. 10,the dose dial sleeve 50′″ and the drive sleeve 60′″ are not inengagement the dose dial sleeve 50′″ is able to rotate with respect tothe drive sleeve 60′″. Conveniently, the clutch means comprises aplurality of radially extending longitudinally directed teeth providedrespectively on the radial flange 94 of the dose dial sleeve 50′″ andthe step 66′″ of the drive sleeve 60′″. When the dose dial sleeve 50′″and the drive sleeve 60′″ are not forced together the respective teethwill ride over one another.

Example 2

In another embodiment of the invention (FIG. 11) there is seen a drivemechanism comprising a second main housing 4′ having a first end and asecond end. A cartridge, containing medicinal product, can be mounted tothe first end of the second main housing 4′ and retained by any suitablemeans. The cartridge and its retaining means are not shown in theillustrated embodiment. The cartridge may contain a number of doses of amedicinal product and also typically contains a displaceable piston.Displacement of the piston causes the medicinal product to be expelledfrom the cartridge via a needle (also not shown).

In the illustrated embodiment, an insert 16′ is provided within the mainhousing 4′. The insert 16′ is secured against rotational and axialmotion with respect to the second main housing 4′. The insert 16′ isprovided with a threaded circular opening extending therethrough.Alternatively, the insert may be formed integrally with the second mainhousing 4′.

An internal housing 154 is also provided within the second main housing4′. The internal housing 154 is secured against rotational and axialmotion with respect to the second main housing 4′. The internal housing154 is provided with a circular opening extending through its length inwhich a series of longitudinally ‘directed splines are formed. A helicalthread 150 extends along the outer cylindrical surface of the internalhousing 154. Alternatively, the internal housing may be formedintegrally with the second main housing 4′ and/or with the insert 16′.

A first thread 19′ extends from a first end of a piston rod 20″. Thepiston rod 20″ is of generally circular section. The first end of thepiston rod 20″ extends through the threaded opening In the insert 16′and the first thread 19′ of the piston rod 20″ is engaged with thethread of the insert 16′. A pressure foot 22″ Is located at the firstend of the piston rod 20″. The pressure foot 22″ is disposed to abut acartridge piston (not shown). A second thread 24′ extends from a secondend of the piston rod 20″. The first thread 19′ and the second thread24′ are oppositely disposed.

A drive sleeve 30′ extends about the piston rod 20″. The drive sleeve30′ is generally cylindrical. The drive sleeve 30′ is provided at afirst end with a first radially extending flange 32″. A second radiallyextending flange 34′ is provided, spaced a distance along the drivesleeve 30′ from the first flange 32″. An external helical thread (notshown) Is provided on the outer part of the drive sleeve 30′ Wendingbetween the first flange 32″ and the second flange 34′. An internalhelical thread extends along the internal surface of the drive sleeve30′. The second thread 24′ of the piston rod 20″ is engaged with theinternal helical thread of the drive sleeve 30′.

A nut 40′ is located between the drive sleeve 30′ and the internalhousing 154, disposed between the first flange 32″ and the second flange34′ of the drive sleeve 30′. The nut 40′ can be either a ‘half-nut or a‘full-nut’. The nut 40′ has an internal thread that is engaged with theexternal helical thread of the drive sleeve 30′. The outer surf-ace ofthe nut 40′ and an internal surface of the internal housing 154 arekeyed together by means of longitudinally directed splines to preventrelative rotation between the nut 40′ and the internal housing 154,while allowing relative longitudinal movement therebetween.

A clicker 50′″ and a clutch 60′″ are disposed about the drive sleeve30′, between the drive sleeve 30′ and the internal housing 154.

The clicker 50″″ is located adjacent the second flange 34′ of the drivesleeve 30′. The clicker 50″″ includes at least one spring member (notshown). The clicker 50″″ also includes a set of teeth (not shown) havinga triangular profile disposed towards the second end of the drivemechanism. When compressed, the at least one spring member of theclicker 50″″ applies an axial force between the flange 34′ of the drivesleeve 30′ and the clutch 60″″. The outer surface of the clicker 50″″and an internal surface of the internal housing 164 are keyed togetherby means of longitudinally directed splines to prevent relative rotationbetween the clicker 50″″ and the internal housing 154, while allowingrelative longitudinal movement therebetween.

The clutch 60″″ Is located adjacent the second end of the drive sleeve30′. The clutch 60″″ is generally cylindrical and is provided at itsfirst end with a plurality of teeth of triangular profile disposed aboutthe circumference (not shown), that act upon the teeth of the clicker50″″. Towards the second end of the clutch 60″″ there is located ashoulder 158. The shoulder 158 of the clutch 60″″ is disposed betweenthe internal housing 154 and a radially inwardly directed flange of thedose dial grip 76′ (described below). The shoulder 158 of the clutch60″″ is provided with a plurality of dog teeth (not shown) extending inthe direction of the second end of the drive mechanism. The clutch 60″″is keyed to the drive sleeve 30′ by way of splines (not shown) toprevent relative rotation between the clutch 60″″ and the drive sleeve30′.

A dose dial sleeve 70′″ is provided outside of the internal housing 154and radially inward from the second main housing 4′. A helical thread isprovided on an inner surface of the dose dial sleeve 70′″. The helicalthread of the dose dial sleeve 70′″ is engaged with the helical thread150 of the internal housing 154.

The second main housing 4′ is provided with a window (not shown)through. which part of the outer surface of the dose dial sleeve 70″ maybe viewed. Conveniently, a visual indication of the dose that may bedialed, for example reference numerals (not shown), is provided on theouter surface of the dose dial sleeve 70′″. Conveniently, the window ofthe second main housing 4′ allows only the dose that is currently dialedto be viewed.

A dose dial grip 76′ is located towards the second end of the drivemechanism. The dose dial grip 76′ is secured against rotational andaxial motion within respect to the dose dial sleeve 70′″. The dose dialgrip 76′ is provided with a radially inwardly directed flange 160. Theradially inwardly directed flange 160 of the dose dial grip 76′ isprovided with a plurality of dog teeth (not shown) extending in thedirection of the first end of the drive mechanism to abut the dog teethof the clutch 60″″. Coupling and decoupling of the dog teeth of the dosedial grip 76′ with the dog teeth of the clutch 60″″ provides areleasable clutch between the dose dial grip 76′ and the clutch 60″″.

A button 82′ of generally ‘T’ shaped cross-section is provided at asecond end of the drive mechanism. A cylindrical feature of the button82′ extends towards the first end of the drive mechanism, through anopening in the dose dial grip 76′ and into a recess in the drive sleeve30′. The cylindrical feature of the button 82′ is retained for limitedaxial movement In the drive sleeve 30′ and against rotation with respectthereto. The cylindrical feature of the button 82′ has lugs extendingradially (not shown) that abut the second surface of the shoulder 158 ofthe clutch 60″″. The second end of the button 82′ is generally circularand has a cylindrical skirt about its periphery that descends towardsthe first end of the drive mechanism. The skirt of the button 82′ islocated radially inward from the dose dial grip 76′.

Operation of the drive mechanism in accordance with the presentinvention will now be described.

To dial a dose, a user rotates the dose dial grip 76′. The spring memberof the clicker 50″″ applies an axial force to the clutch 60″″ in thedirection of the second end of the drive mechanism. The force exerted bythe spring member of the clicker 60″″ couples the dog teeth of theclutch 60″″ to the dog teeth of the dose dial grip 76′ for rotation. Asthe dose dial grip 76′ is rotated, the associated dose dial sleeve 70″″,the drive sleeve 30′ and the clutch 60″″ all rotate in unison.

Audible and tactile feedback of dose being dialed is provided by theclicker 50″″ and the clutch 60″″. As the clutch 60″″ is rotated, torqueis transmitted from the teeth at the first end of the clutch 80″ and theteeth of the clicker 50″″. The clicker 50″″ cannot rotate with respectto the internal housing 154, so the at least one spring member of theclicker 50″″ deforms allowing the teeth of the clutch 60″″ to jump overthe teeth of the clicker 50″″ producing an audible and tactile ‘click’.Preferably, the teeth of the clicker 50″″ and the teeth of the clutch60″″ are disposed such that each ‘click’ corresponds to a conventionalunit of the medicinal product, or the like.

The helical thread of the dose did sleeve 70″″ and the internal helicalthread of the drive sleeve 30′ have the same lead. This allows the dosedial sleeve 70′″ to advance along the thread 150 of the internal housing154 at the some rate as the drive sleeve 30′ advances along the secondthread 24′ of the piston rod 20″.

Rotation of the piston rod 20″ is prevented due to the opposingdirection of the first thread 19′ and the second thread 24′ of thepiston rod 20″. The first thread 19′ of the piston rod 20″ is engagedwith the thread of the insert 16′ and so the piston rod 20″ does notmove with respect to the second main housing 4′ while a dose is dialed.

The nut 40′, keyed to the internal housing 154, is advanced along theexternal thread of the drive sleeve 30′ by the rotation of the drivesleeve 30′. When a user has dialed a quantity of medicinal product thatis equivalent to the deliverable volume of the cartridge, the nut 40′reaches a position where it abuts the second flange 34′ of the drivesleeve 30′. A radial stop formed on the second surface of the nut 40′contacts a radial stop on the first surface of the second flange 34′ ofthe drive sleeve 30′, preventing both the nut 40′ and the drive sleeve30′ from being rotated further.

Should a user inadvertently dial a quantity greater than the desireddosage, the drive mechanism allows the dosage to be corrected withoutdispense of medicinal product from the cartridge. The dose dial grip 78′is counter-rotated. This causes the system to act in reverse. The torquetransmitted through the clutch 60″″ causes the teeth at the first end ofthe clutch 60″″ to ride over the teeth of the clicker 50″″ to create theclicks corresponding to the dialed dose reduction.

When the desired dose has been dialed, the user may then dispense thisdose by depressing the button 82′ In the direction of the first end ofthe drive mechanism. The lugs of the button 82′ apply pressure to thesecond surface of the shoulder 158 of the clutch 60″″, displacing theclutch 60″″ axially with respect to the dose dial grip 76′. This causesthe dog teeth on the shoulder 168 of the clutch 60″″ to disengage fromthe dog teeth of the dose dial grip 76′. However, the clutch 60″″remains keyed in rotation to the drive sleeve 30′. The dose dial grip76′ and associated dose dial sleeve 70′″ are now free to rotate (guidedby the helical thread 150 of the internal housing 154).

The axial movement of the clutch 60″″ deforms the spring member of theclicker 50″ and couples the teeth at the first and of the clutch 60″ tothe teeth of the clicker 50″ preventing relative rotation therebetween.This prevents the drive sleeve 30′ from rotating with respect to theinternal housing 154, though it is still free to move axially withrespect thereto.

Pressure applied to the button 82′ thus causes the dose dial grip 76′and the associated dose dial sleeve 70′″ to rotate into the second mainhousing 4′. Under this pressure the clutch 60″″, the clicker 50″″ andthe drive sleeve 30′ are moved axially In the direction of the first endof the drive mechanism, but they do not rotate. The axial movement ofthe drive sleeve 30′ causes the piston rod 20″ to rotate through thethreaded opening In the insert 16′, thereby to advance the pressure foot22″. This applies force to the piston, causing the medicinal product tobe expelled from the cartridge. The selected dose is delivered when thedose dial grip 76′ returns to a position where It abuts the second mainhousing 4′.

When pressure Is removed from the button 82′, the deformation of thespring member of the clicker 50″″ is used to urge the clutch 60″″ backalong the drive sleeve 30′ to re-couple the dog teeth on the shoulder158 of the clutch 60″″ with the dog teeth on the dose dial grip 76′. Thedrive mechanism is thus reset in preparation to dial a subsequent dose,

The invention claimed is:
 1. A drug delivery drive mechanism,comprising: an first housing; a second housing configured to reside atleast partially internally to said first housing; a dial sleeve providedoutside of said second housing and radially inward from said firsthousing, said dial sleeve threadedly engaged to said second housing; adrive sleeve coupled to said dial sleeve; and a piston rod threadedlyengaged to said drive sleeve wherein during a dose setting step, saiddial sleeve and said drive sleeve translate in a proximal direction awayfrom said second housing.
 2. The drug delivery drive mechanism of claim1 wherein during a dispensing step, said dial sleeve moves in a distaldirection towards said second housing.
 3. The drug delivery device ofclaim 2 wherein during the dispensing step, said drive sleeve moves insaid distal direction so as to drive said piston rod.
 4. The drugdelivery drive mechanism of claim 1 wherein said piston rod comprises afirst thread and a second thread.
 5. The drug delivery drive mechanismof claim 4 wherein said first thread of said piston rod engages athreaded insert, so that during a dispensing step, said piston rodrotates as it moves in a distal direction.
 6. The drug delivery drivemechanism of claim 5 wherein said threaded insert is formed integrallywith said first housing.
 7. The drug delivery drive mechanism of claim 4wherein said second thread of said piston rod threadedly engages saiddrive sleeve.
 8. The drug delivery drive mechanism of claim 7 wherein athread of said drive sleeve and said thread of said dial sleeve have thesame lead.
 9. The drug delivery drive mechanism of claim 1 furthercomprising a clutch, said clutch releasably engaging said dial sleeveand said drive sleeve.
 10. The drug delivery drive mechanism of claim 9wherein said clutch is keyed in rotation to said drive sleeve.
 11. Thedrug delivery drive mechanism of claim 1 wherein said drive sleevecomprises a first radially extending flange and a second radiallyextending flange, said second radially extending flange spaced adistance along said drive sleeve from said first flange.
 12. The drugdelivery drive mechanism of claim 11 wherein said drive sleeve furthercomprises an external helical thread, said external helical threadprovided along an outer portion of said drive sleeve, said externalhelical thread extending between the first flange and said secondflange.
 13. The drug delivery drive mechanism of claim 12 furthercomprising a non-rotating member disposed between said first flange andsaid second flange of said drive sleeve, said non-rotating membercomprising a thread that threadedly engages said external thread of saiddrive sleeve.
 14. The drug delivery drive mechanism of claim 13 whereinduring said dose setting step, said non-rotating member advances alongsaid external thread of said drive sleeve during rotation of said drivesleeve such that when a quantity of product that is equivalent to adeliverable volume of a cartridge is selected, said member abuts saidfirst or said second flange of said drive sleeve.
 15. The drug deliverydrive mechanism of claim 14 wherein said second housing portioncomprises a plurality of longitudinally directed splines, saidlongitudinally directed splines keyed to an outer surface of saidnon-rotating member.
 16. The drug delivery drive mechanism of claim 1further comprising a clicker disposed about said drive sleeve, such thatsaid clicker provides audible feedback during said dose setting step.17. The drug delivery drive mechanism of claim 1 further comprising adial grip, said dial grip secured against rotational and axial motionwith respect to said dial sleeve.
 18. The drug delivery device mechanismof claim 17 wherein during said dose setting step, said dial grip isrotatable in a first direction to set a first dose and is also rotatablein a second direction to set a second dose wherein said second dose isless than said first dose.
 19. The drug delivery drive mechanism ofclaim 1 wherein an inner portion of said dial sleeve threadedly engagesan outer portion of said second housing.